A power transmission apparatus is installed in a two-wheeled vehicle, such as a bicycle or a motorcycle. The power transmission apparatus provides transmission power using a motor or the like in order to realize high driving force by using little power.
The power transmission apparatus utilizes a gear system to maximize the output of the motor and the speed change is possible by driving the motor in the forward or reverse direction.
However, according to the power transmission apparatus of the related art, the driving force of the motor is converted by using a pin or a spring, so many components are necessary and the assembling process is complicated, resulting in the degradation of the durability and reliability.